Such devices as an inkjet recording device, etc., is known as an image forming device for a printer, a facsimile machine, a reproducing unit, a plotter, and a multifunctional unit having these functions, and as a liquid ejection recording-type image forming device which uses a recording head including a liquid ejection head (a liquid droplet ejection head) that ejects ink droplets, for example. The liquid ejection recording-type image forming device ejects ink droplets from a recording head to a sheet to be conveyed (not limited to paper and includes an OHP sheet, representing what the ink droplets and other liquid, etc., can adhere to; also called a medium to be recorded on, or a recording medium, recording paper, a recording sheet) to perform image forming (recording, print, imaging, printing also used interchangeably). The liquid ejection recording-type image forming device includes a serial-type image forming device which ejects liquid droplets while the recording head moves in a main scanning direction to perform image forming and a line-type image forming device with the use of a line-type head which ejects liquid droplets while the recording head does not move to perform image forming.
Herein, the liquid ejection recording-type “image forming device” represents a device which ejects droplets to a medium such as paper, thread, fiber, cloth, leather, metal, plastic, glass, wood, ceramics, etc., while “image forming” represents not only providing a medium with an image which has a meaning, such as a character or graphics, but also providing a medium with an image which does not have a meaning, such as a pattern (merely causing a droplet to impact the medium). Moreover, “ink” is not limited to what is called ink, but all types of liquids which allow image forming, such as what is called recording liquid, fixing solution, liquid, etc., and also includes DNA samples, resist, pattern material, resin, etc., for example. Furthermore, “image” is not limited to a planar image, but also an image provided to what is formed three-dimensionally, and also an image formed by three-dimensionally shaping a solid itself.
Now, a liquid ejection-type image forming device includes a maintaining and restoring unit (a restoring unit) which includes a wiper member (also called a wiper blade, a wiping blade, a blade, etc.) which wipes off a nozzle face of a recording head to clean the nozzle face; and a cap which caps the nozzle face of the recording head in order to maintain ejection stability of a nozzle of the recording head, to prevent ink in the nozzle from drying and to prevent dust from entering into the nozzle, wherein the maintaining and restoring operation (a maintaining operation) is performed which, for instance, after draining thickened ink from the nozzle into the cap, wipes off the nozzle face with the wiper member to form a nozzle meniscus.
Herein, with respect to the timing of performing restoring operations, an apparatus is known which includes restoring processing units which can individually execute restoring operations for keeping good ink ejecting states of each of a first group of nozzle arrays and a second group of nozzle arrays using a recording head which includes the first group of nozzle arrays and the second group of nozzle arrays that eject liquid droplets of different colors; and a restoring control unit, wherein, responsive to determining that a condition for executing a restoring process is satisfied for at least one group of nozzle arrays out of the first group of nozzle arrays and the second group of nozzle arrays, the restoration control unit conducts control such that the restoring process for the condition-satisfying nozzle array group is executed, while, responsive to determining that a predetermined condition prior to when the condition for executing the restoring process has been satisfied is satisfied for the other group of nozzle arrays, the restoration control unit conducts control such that the restoring process for the other nozzle array group is executed (Patent Document 1).
It is also known to perform restoring operations on all of the recording heads when a rest time of an apparatus reaches a predetermined time or when a consecutive printing time or the number of consecutive print sheets reaches a predetermined value.
Patent Document
Patent Document 1: JP2005-238711A
Now, when an apparatus which performs a large amount of printing, such as a line-type image forming apparatus, for example, is provided with a black recording head and a color recording head and is provided with a restoring unit which performs a restoring operation independently for each of the heads, if it is arranged for executing the restoring operation when a cumulative number of print sheets reaches a predetermined number, for example, a situation arises such that the restoring operation for the color recording head is performed in a short period of time after the restoring operation of the black recording head is performed.
Now, it is possible to apply a technique disclosed in Patent document 1, so that, if a cumulative number of print sheets for one recording head reaches a predetermined number of sheets, even when the cumulative number of print sheets for the other recording head does not reach the predetermined number of sheets, but predetermined conditions are satisfied, the restoring operation is performed for both the black recording head and the color recording head.
However, in such a configuration, the restoring operation is not performed as long as the cumulative number of print sheets does not reach a predetermined number of sheets for either of the recording heads, which is not satisfactory for executing the restoring operation at an appropriate timing and, moreover, is not satisfactory from a point of view of improving throughput by reducing the number of times of restoring operations.